Ion source slit cleaner for calutron



May 26, 1959 Filed June 28, 1946 E. O. LAWRENCE ION SOURCE SLIT CLEANER FOR CALUTROIN 2 Sheets-Sheet 1 wie mmNToR. ffm/fsf 0 AWM-w65 ATTORNEY.

May 26, 1959. E. o. LAWRENCE 2,888,566

- ION SOURCE SLIT CLEANER FOR CALUTRON Filed June 28, 1946 2 Sheets-Sheet 2 59 @ig/3- S ff/ /2/ y /3/ mmmm. 3P/V557 O. AWM-WCE ATTORNEY.

arent i 2,888,566 Patented Mar. 261 1959 2,888,566 l IoN SOURCE sur CLEANER Fon CALUTRON v Application June 28, 1946, Serial No. 679,881

13 Claims. (Cl. Z50-41.9)

The present invention relates to means for generating a beam of ions and, more particularly, to such an ion transmitter for use in what is known in the art as the Calutron A calutron is a term which has been deiined as any apparatus or machine wherein isotope separation or enrichment is achieved on a large scale, using commercially useful quantities of one or more isotopes by appropriate separative action on gaseous ions with electrostatic or electromagnetic means or combinations of them. The foregoing definition has been taken from U.S. Patent No. 2,709,222 for Method and Apparatus for Separating Materials, issued May 24, 1955 to Ernest O. Lawrence. In that application, the theory of ionic separation and the principles of operation of a calutron are so fully treated and thoroughly explored that no useful purpose would be served by here repeating the discussion contained therein.

It may be stated in passing, however, that by projecting a beam of positive ions of a vaporized or gaseous polyisotopic substance through an evacuated receptacle disposed in a magnetic field acting normally to the path of the beam, the beam is caused to follow a curve wherein the ions of the heavier isotope tend to concentrate in the region adjacent the outer periphery and the ions of the lighter isotope congregate in the region adjacent the inner periphery. In other words, ions of greater mass travel along a curve of greater radius than the ions of lesser mass. By disposing suitable pockets or collectors in the path of beam, preferably 180 from the source of the beam, it is possible to collect at least two masses, one of which is enhanced with respect to one isotope while the other is correspondingly impoverished with respect thereto.

Of course, there are many conditions which must be fulfilled before a calutron can be successfully operated. For example, the ion source, the region surrounding the beam, and the collector must be incorporated in a reduced pressure system evacuated to a pressure of the order of -5 to 10-4 mm. Hg. Such matters will be herein referred to but briefly, inasmuch as it is with the ion beam producing mechanism, or source, that the present invention is concerned.

A source for a calutron includes a chamber for holding a quantity of material capable of being vaporized, a heater for the chamber, a cathode and anode for establishing an arc discharge, and accelerating electrodes; the arrangement is such that when the circuits are closed, the material vaporizes and is drawn through the electron stream of the arc where dissociation and ionization take place. The ions are then drawn through a slit by the accelerating electrodes to form a beam.

The operation of such a calutron accordingly requires the vaporization of the material to be ionized and, consequently, the problem is created of cleaning various operative parts of the device which may be encrusted with condensed vapors. To this end, the present inventioncontemplates a calutronv source embodying an improved device for cleaning the source mechanism from encrusted materials. Y

lt is accordingly the further object of this invention to produce an ion beam more efliciently by insuring removal of encrusted materials from the beam defining elements of the ion source.

It is another object of this invention to increase the time during which a calutron may be operated by eliminating shut-downs due to the encrusting of the source mechanism by condensed vapors.

An important feature of this invention consists in providing in the source mechanism suitable cleaning elements which can be actuated periodically by the operator to remove encrusted material from the source slits.

It is a further feature of this invention to utilize the above-mentioned scraping unit to form the anode of the ion generator mechanism.

Further objects, advantages and features will be apparent from the annexed specification, in which:

Figure 1 is an isometric perspective of an ion source, embodying the present invention;

Fig. 2 is an isometric perspective of the scraper block employed in this invention;

Fig. 3 is a side elevation, partly in section, of a calutron embodying the present invention; and

Fig. 4 is a section taken on the line 4-4 of Fig. 3.

Referring more particularly to the drawings, there is illustrated a calutron, including an electromagnet (not shown) having an upper pole piece 10 and a lower pole piece 11, between which is positioned a Vessel 12 adapted to be evacuated by suitable pumps (not shown) to a pressure of the order of 10-4 to 10-5 mm. Hg.

The vessel 12 includes a bottom wall 13, a top wall 14, and a removable front wall or door 15. Mounted on the removable door 15 and projecting into the vessel 12 is an ion generating and transmitting mechanism indicated generally at 16. The ion generating mechanism 16 includes a suitable charge reservoir 17 within which is positioned a removable charge bottle 18 which is adapted to be lled with a suitable charge material which, when heated by a heater (not shown), will vaporize.

A suitable material for this purpose is uranium tetrachloride. The charge reservoir 17 is provided with a nipple 19 communicating the charge bottle 18 to a manifold 20. The manifold 20, as shown, includes a passage 21 and a passage 22 in which are mounted baiiies 23 adapted to break up the ow of vapors and insure a uniform distribution thereof.

The source unit 16 also includes ionizing chambers 24 which take the form of elongated vertically extending slots. The ionizing chambers 24 are each provided with a longitudinal slit 25 defined by a pair of slit-delining elements 27 projecting into the chambers 24. Chambers 24 are also each provided with a pair of elongated panels 28 which serve the function of electron traps or as slots to shape the arc plasma. The source 16 also includes a pair of cathode stems 29 having their end portions 30 overlying the top of the chambers 24 and in which are positioned suitable electron emissive cathodes (not shown). As indicated, the cathode stems 29 extend through a suitable aperture in the front door 15 and are connected to bushings 31 mounted in sealing relation to the door 15. The door 15 also carries a bushing 32 supporting the source unit 16, as shown.

The source unit 16 includes brackets 33 in which are journaled a pair of upstanding guide rods 34. Each of the guide rods 34 is provided with a sleeve 35 mounted for longitudinal movement thereon. Sleeves 35 are provided with a pair of opposed sockets 36 in which is situated a transverse rod 37. A pair of blocks or scrapers 38 are provided, joined to the transverse rod 37 by means of arms 40 rigidly secured thereto. The arms 40 may be secured to the blocks 38 by pins 41 as clearly illustrated in Fig. 2. As illustrated, the blocks 38 are provided with a tapered upper side 42 and with a T-shaped rear end 43 forming slots 44. The end 43 as well as the slots 44 are adapted to fit within the chamber 24, and in close engagement with the slit defining shoulders 27.

Each of the sleeves 35 is provided with a pin 45 on which is pivoted one end of a link 46. The links 46 carry pins 47 on which are pivoted arms 48 of a bell crank 49. The other arm of the bell crank 49 is cennected by means of a pin 50` to link 5f. which is in turn connected by a pin 52 to a push rod 53. Brackets 54 are mounted on the rear side of the door 15 providing bearings 55 for a transverse rod 56 forming the pivot of the bell crank 49. The push rod 53 has its rear end positioned in a bracket 57, mounted on the source unit 316, as shown. The outer end of the push rod 53 engages a rod 58 positioned in a suitable aperture 59 in the door i5. The door i has a Wilson seal 6i) affixed in vacuum-tight relation thereto, and the rod 58 extends through the Wilson seal 60, as indicated.

As is Well understood, the Wilson seal 60 is provided on its interior with means permitting the longitudinal movement of the rod 58 without breaking the vacuum seal.

As indicated in Figs. 3 and 4, the calutron contemplated includes a pair of accelerating members 6l in alignment with the beam defining slits 25 and an electrostatic sheet or liner 62 may be provided on which the members 6i are mounted.

When the ion generating mechanism indicated is operated, the charge material in the charge bottle f8 is heated in any suitable means, causing the charge material to vaporize, the vapors thus generated will pass through the nipple 19 into the manifold 20, through the baiiies 23, and into the chambers 24. The electron emissive cathodes are energized to cause a stream of ions to flow from the cathodes to the anodes, which in this case are formed by the blocks 38. As will be well understood, the electromagnet has been energized to cause a strong substantially uniform magnetic flux to pass through the entire vessel 12, and this magnetic field serves to collimate the streams of electrons within the chambers 24 and cause them to take a path longitudinal of the slots 25 and to finally engage the anodes 33.

The arc thus generated serves to ionize the vapors and a stream of ions is caused to flow through the slits Z5 by the accelerating members ai which are maintained at a high negative potential with respect to the source mechanism 16, which is grounded. During the above described operation, certain of the vapors will condense, particularly in the region of the chambers 24, and thc slits 25. lf allowed to condense, the resulting encrustation would alter the characteristics of the slits 2S and eventually obstruct them, necessitating a shutting down of the calutron. Accordingly, the blocks 3S are provided Which, by reason of the linkage formed by the rods 58 and 53, the links 5l, the bell crank 49 and the links 46, engaging the sleeves 35, are mounted for longitudinal movement Within the chambers 24. Actuating this longitudinal movement causes the blocks 38 to travel the full length of the chambers 24 and the slits 25 and scrapes off any encrusted material.

lt `)vill be apparent from the foregoing description that there is provided suitable mechanism for prolonging the operation of the caiutron unit by cleaning off encrusted material, and also this mechanism serves to prevent such encrusted material from altering the shape and hence the characteristics of the beam defining slits.

While there is disclosed what is at present considered a preferred embodiment of the invention, it will be understood that various changes and modifications may be made therein. and it is intended to cover all such @l as come Within the true spirit and scope of the appended claims.

What is claimed is:

1. Apparatus for projecting an ionic beam comprising an ion generating chamber having a beam defining slit therein, and a block mounted in said slit for longitudinal movement therein, and means for actuating longitudinal movement of said block.

2. Apparatus for projecting an ionic beam comprising an ion generating chamber having a beam defining slit therein, and a block mounted in said slit for longitudinal movement therein, and linkage means for actuating longitudinal movement of said block.

3. Apparatus for projecting an ion beam comprising Walls defining an evacuated vessel, an ion generating chamber having a beam defining slit therein mounted within said Vessel, a block mounted for longitudinal movement within said slit and linkage including a push rod extending through one of said walls for actuating longitudinal movement of said block.

4. Apparatus for projecting an ion beam comprising Walls defining an evacuated vessel, an ion generating chamber having a beam defining slit therein mounted Within said vessel, a block mounted for longitudinal movement Within said slit and linkage including a push rod extending through one of said Walls for actuating longitudinal movement of said block, and means forming a vacuum tight seal around said push rod.

5. A calutron comprising walls defining an evacuated vessel, an ion transmitter mounted in said vessel and including an ionizing chamber having a beam defining slit therein, a scraper mounted for longitudinal movement in said slit, and operating means associated with said scraper for actuating said scraper to clean said slit.

6. A calutron comprising Walls defining an evacuated vessel, an ion transmitter mounted in said vessel and including an ionizing chamber having a beam defining slit therein, a pair of guide rods adjacent said slit and spaced apart on opposite sides thereof, a scraper supporting member mounted for longitudinal movement on said guide rods, a scraper carried by said member and positioned in said slit, and linkage mechanism adapted to actuate said scraper to clean said slit.

7. A calutron comprising Walls defining an evacuated vessel, an ion transmitter mounted in said Vessel and including an ionizing chamber having a beam defining slit therein, a pair of guide rods adjacent said slit and spaced apart on opposite sides thereof, a scraper supporting member mounted for longitudinal movement on said guide rods, a scraper carried by said member and positioned in said slit and linkage mechanism adapted to actuate said scraper to clean said slit, said linkage mechanism including a push rod extending through one of said Walls.

8. A calutron comprising Walls defining an evacuated vessel, an ion transmitter mounted in said vessel and including an ionizing chamber having a beam defining slit therein, a pair of guide rods adjacent said slit and spaced apart on opposite sides thereof, a scraper supporting member mounted for longitudinal movement on said guide rods, a scraper carried by said member and positioned in said slit and linkage mechanism adapted to actuate said scraper to clean said slit, said linkage mechanism including a push rod extending through one of said Walls, and a vacuum seal mechanism associated with said push rod.

9. A calutron comprising Walls defining an evacuated vessel, an ion transmitter mounted in said vessel and including an ionizing chamber having a beam defining slit therein, an electron-emissive cathode aligned with said chamber, a block mounted in said chamber and in said slit and constituting an anode, and means for moving said block longitudinally in said slit to clean said slit.

l0. A calutron comprising walls defining an evacuated vessel, an ion transmitter mounted in said vessel and including an ionizing chamber having a beam defining slit therein, an electron emissive cathode aligned with said chamber, a block mounted in said chamber and in said slit and constituting an anode, and means for moving said block longitudinally in said slit to clean said slit, said last mentioned means including linkage mechanism for actuating movement of said block.

11. A calutron comprising walls defining an evacuated vessel, an ion transmitter mounted in said vessel and including an ionizing chamber having a beam defining slit therein, an electron emissive cathode aligned with said chamber, a block mounted in said chamber and in said slit and constituting an anode, and means for moving said block longitudinally in said slit to clean said slit, said last mentioned means including linkage mechanism for actuating movement of said said block, and a push rod extending through one of said walls and cooperating with said linkage mechanism.

12. A calutron comprising walls defining an evacuated vessel, an ion transmitter mounted in said vessel and including an ionizing chamber having a beam dening slit therein, an electron emissive cathode aligned 'with said chamber, a block mounted in said chamber and in said slit and constituting an anode, and means for moving said block longitudinally in said slit to clean said slit, said last mentioned means including linkage mechanism for actuating movement of said block and a push rod extending through one of said walls and cooperating with said linkage mechanism, and vacuum seal mechanism associated with said push rod.

13. In combination with an ion transmitter enclosed in an evacuated vessel and including an ionizing chamber having a beam defining slit therein and an electron emissive cathode aligned with said chamber; encrustation temoval means adapted to clean the beam defining slit and comprising a scraper block mounted within said chamber and extending through said slit in intimate slidable contact with the defining walls thereof, a pair of guide rods rigidly mounted upon the ion transmitter adjacent and parallel to the beam defining slit, a sleeve member slidably mounted on each of said guide members, a support rod rigidly secured to each of said sleeves and disposed transversely to said slit, a mounting pin rigidly secured to said support rod and pivotably engaging said scraper block whereby translation of said sleeves along said guide rods advances said scraper block along said slit in close engagement therewith, and mechanical motion producing means including a bell crank having a rotatable mounted shaft and three arms rigidly fixed thereto in perpendicular relation with the lirst two of said arms being parallel and disposed at opposite ends of said shaft and the third of said arms forming an acute angle with said first two arms, a slidably mounted push rod engaging the third of said bell crank arms in driving relation thereto, and linking means pivotably connecting the first two of said bell crank arms one to each of said slidably mounted sleeves whereby said sleeves are urged along said guide rods in response to actuation of said push rod and said 25 beam defining slit is cleared of encrustation.

References Cited in the file of this patent UNITED STATES PATENTS 2,059,139 Neher et al. Oct. 27, 1936 2,089,821 Raisch July 13, 1937 2,221,467 Bleakney Nov. 12, 1940 2,305,935 Thom Dec. 22, 1942 

